[Resolved] Unable to post anything except unformatted text

When creating a post whenever I try to format the text with in either Visual or HTML mode and press preview or update it sends me to the index page of my domain and the formatting changes are not accepted. I have tried deactivating visual mode, changing themes, deactivating all plugins, but nothing seems to work.

I disabled gears and deactivated all plugins. I disabled the visual editor too. The issue still persists…whenever I try anything other than simple text, it will not accept the formatting and the preview sends me to the root index page of my domain. Very unusual and extremely frustrating. Any other suggestions?

Thanks so much for your help. It is still not working. tried several times to rename the plugins folder. It does not solve my problem. I actually deleted the entire installation and started again from scratch and still the same issue. I just want to have the capability to format my posts…Could it possibly be an issue my web host?